I'm an amateur news photographer and had the EF 24-70mm f/2.8L for a while attached to my 30D. The "brick" was a true friend, a lens I couldn't say enough good things about: it's build and glass is worth the price. Although, I just purchased the EOS 5D and the 24-105mm f/4L IS USM came with it. I reluctantly sold the brick and took my chances with this kit lens. All I have to say is, whew! This lens rocks for what I use it for. Like other reviewers here who were skeptical about the f/4, have no fear, the extra stops the IS buys you is remarkable. I shoot street and various interiors for events, and with its range, this babe delivers (let me also say that this is also largely due to it being attached to the full frame 5D). An f/2.8 would be better no doubt, but the IS is a life saver for photojourno work. I also purchased the 70-200mm f/2.8L IS USM, and with this duo, I rest easier.